Thread cutting device for single thread chain stitch sewing machine



c. J. M. BENINK ET A1. 2,858,786 THREAD CUTTING DEVICE FOR SINGLE THREAD 0mm STITCH SEWING MACHINE Nov. 4 1958 4 Sheets-Sheet 1 Filed Sept. 30. 1957 Nov. 4, 1958 c. J. M. BENINK ETAL 2,853,785

THREAD CUTTING DEVICE FOR SINGLE THREAD CHAIN STITCH SEWING MACHINE Filed Sept. 30, 1957 4 Sheets-Sheet 2 FIG-E lNVENTORS (br/Isfiaarr \Zxseph Mar/nus BfN/N/s and Reinhold .DOBNEP Nov. 4, 1958 c. J. M. BENINK EIAL 2,858,785

THREAD CUTTING DEVICE FOR SINGLE THREAD CHAIN STITCH SEWING MACHINE Filed Sept. C50, 1957 4 Sheets-Sheet 3 INVENI'OPS Nov. 4, 1958 c. J. M. BENINK ETAL THREAD CUTTING DEVICE FOR SINGLE THREAD CHAIN STITCH SEWING MACHINE Filed Sept. 50, 1957 4 Sheets-Sheet 4 and Pe/n/m/o' 003N679 THREAD CUTTING DEVICE FOR SINGLE THREAD CHAIN STITCH SEWING MA- CHINE Christiaan Joseph Marinus Benink and Reinhold Dobner, Kaiserslantern (Pfalz), Germany, assignors to G. M. Pfatf A. G., Kaiserslautern (Pfalz), Germany Application September 30, 1957, Serial No. 687,199 Claims priority, application Germany October 11, 1956 3 Claims. (Cl. 112-252) The present invention relates to single thread chain stitch sewing machines and is particularly concerned with a thread cutting device for single thread chain stitch sewing machines having a guided auxiliary looper.

In chain stitch sewing machines, particularly button fastening machines, special thread cutting devices are frequently waived for the sake of simple construction of the machine and the thread is permitted to tear off after completion of the work by simply raising the button clamp. This manner of thread severing is not suitable for thin materials.

It is an object of the invention to provide a simple thread cutting device which operates automatically and which does not have any additional, space consuming parts below the stitch plate.

In accordance with the invention the auxiliary looper is provided with a thread cutter which, after the auxiliary looper having been shifted from its loop catching position to severing position becomes operative by a pivotal movement of the auxiliary looper.

In machines provided with means for automatic interruption of operations, the guiding of the auxiliary looper carrying the thread cutter may take place by the stopping mechanism in a manner to cause automatic thread cutting.

Thus, in accordance with the invention a thread cutting device for single thread chain stitch sewing machines of the type having an auxiliary looper is characterized in that the auxiliary loo-per is provided with a thread cutter which, after the auxiliary looper has been moved from its loop catching position into cutting position, becomes operative by the rocking movement of the auxiliary looper.

Additional objects and features of the invention and details of the advantages obtained thereby will become apparent from the following specification with reference to the embodiment of a thread cutting device for a chain stitch sewing machine operating under guided control which is illustrated in the accompanying drawings in which Fig. 1 is an elevational view of a chain stitch sewing machine taken from the left side, partly in cross section,

Fig. 2 is a view of the machine from the operating end,

Fig. 3 is a fractional view taken from the right side of the machine,

Fig. 4 is a perspective view showing details of the thread cutting device,

Fig. 5 is a top view of the auxiliary looper,

Fig. 6 illustrates the auxiliary looper in loop catching position of operation, and

Fig. 7 shows it in the thread cutting position of operation.

The machine illustrated in the drawings comprises a base 1, support arm 2, standard 3, arm 4 and head 5 of a single thread chain stitch machine. The rotary shaft 6 with the chain stitch looper 7 at its forward end United States Patent 6 ice is mounted on the support arm 2 with the auxiliary looper cam 8 disposed below the standard 3. The auxiliary cam lever 10, biased by means of spring 11 against the cam 8 is clamped onto the shaft 9 of the auxiliary looper.

A guiding groove disk 12 (Figs. 2 and 3) provided with shut off cams 13 which cooperate with follow r member 14 of the switch lever 15 is mounted on the right side of the machine. A catch or pawl 16 is supported on the switch lever 18 and cooperates with the lock member 17 'of the switch lever 18 of the machine. The belt guide 19 adapted to shift the drive belt 20 either to the idler pulley 21 or to the drive pulley 22 is connected together with the lock member 23 to the switch lever 18. Supported on drive pulley 22 is a brake disk 24 provided at its tapering side 25' with a groove 25 which cooperate with the lock member 23 for braking and stopping operations.

The auxiliary looper 26 is secured to auxiliary looper shaft 9 and is provided in a known manner with a book 27 secured to auxiliary looper 26 by means of a screw 28 which also secures a cutter 29 to the auxiliary looper on the side opposite to that on which the hook 27 is mounted (Fig.5).

The auxiliary looper shaft 9 is axially movable in the bearing sleeves 30, 31 and 32 which are provided in the support arm 2. A lock ring 33 is secured to the shaft 9 which is biased by a spring 34 against the bearing sleeve 32.

The end of the auxiliary looper shaft 9 which is received in the bearing shell 30 at the rear projects from the base 1 and presents an abutment 35 (Fig. 4). The end of the shaft carries a rotatable dog 36 which is provided with a recess 37 for an abutment key 35 and presents an abutment edge 38 for moving the auxiliary drive shaft 9 by way of key 35. An an'gularly shaped sheet metal member 39 secured to the base 1 is provided to secure the dog 36 which abuts sleeve 30 against displacement axially of the auxiliary shaft 9.

A link 41 is pivotally connected at one end by way of a collar screw 40 to the dog 36 and is biased by means of a tension spring 42. The other end of the link 41 is pivotally connected by means of collar screw 44 to a leg of a bellcrank lever 43, the other leg of which is provided with a bore 45 which threadedly receives a set screw 46 which projects into the path of operation of switch lever 18 and is secured against rotation by means of a. lock nut 47. Bellcrank lever 43 is pivotally mounted by means of a collar screw 48 on a bracket 49 secured to base 1. An angular support member 50 is threadedly secured to the base 1 and a two armed lever 51 is mounted for pivotal movement on said member by means of collar screw 52.

One arm-of the lever 51 has a bore 53 which receives an adjustable screw 55 secured by a lock nut 54 against rotation in a manner that its head is adapted to engage the front end of the auxiliary drive shaft 9 while the other end of the lever 51 is provided with an abutment end 56.

A double armed lever 57 is pivotally mounted on the extended shaft 58 of the switch lever 18 and presents an abutment plane 59 on its downwardly directed arm which is adapted to engage the abutment 56. The upwardly extending arm of lever 57 is biased by a tension spring 60, one end of which is connected to a hook 61 on the standard while the other end is placed around a screw 62 in the upper arm of lever 57. An angular member 63 is threadedly secured to switch lever 18 a set screw being secured to said member by a lock nut 64 against which rests the arm of lever 57 under the tension of the spring 60.

The illustrated embodiment of the invention operates l as follows: After the automatic disconnecting the shut off cam 13 has come to rest immediaely behind the follower member 14. In order to switch on the machine the switch lever 18 is moved clockwise as seen in Fig. l, or counterclockwise as seen in Fig. 3, and causes the machine to operate by way of the belt guide 19 and move lock member 17 to engage catch 16 from below to hold the lever 18 in position of operation. During'the ensuing series of stitches the guiding groove disk 12 continues to rotate slowly.

By way of cam 8 and cam lever the looper shaft 6 applies oscillatory movements to the auxiliary looper shaft 9 and thereby to the auxiliary looper 26 which, under the pressure applied by spring 34 upon the set ring 33 of auxiliary shaft 9 is held in its loop catching position (Fig. 6). Before'entrance of the needle 66 into the material the auxiliary looper 2 6 with its hook 27 grips the loop 67 formed by the previous stitch which is still held by the looper 7 and moves it aside. As a result the needle 66 in moving downwardly safely meets the triangle formed by the thread so that the loop 68 newly formed during the upward movement of the needle can be gripped by the looper 7 and drawn through the preceding loop 67.

The abutment 35 on the auxiliary looper shaft 9 is then outside the recess 37 of the rotatable dog 36. The double armed levers 57 and 51 are in idling position. Upon completion of the sewing work the machine is switched off in a known manner by means of the shut off cams 13 (Fig. 3) on the guiding groove disk 12 which press down the switch lever 15 which causes the catch 16 to slip off the lock member 17 while the lock member 23 of the lever 18 contacts the raised portion of the brake disk 24 during the last half rotation of the drive shaft.

With this movement of the switch lever 18 also the double armed lever 57 (Fig. 4) due to the pull of spring 60 effects a rotary movement which is applied to the double armed lever 51. Thus the head of set screw 55 makes contact with the end of auxiliary looper shaft 9 without displacing the same.

During the further rotation of the arm shaft the lock member 23 comes into contact with the side 25 of the brake disk thus drawing the switch lever 18 closer to the disk. As a result also the double armed levers 57 and51 effect further pivotal movements and the auxiliary looper shaft 9 is pushed forward axially against the force of spring 34 and thus the cutter 29 on the auxiliary looper 26 is moved into operative position.

This angular movement of the switch lever 18 causes the lower arm of the lever to move the dog 36 against the pull of the spring 42 by way of set screw 46, bell crank lever 43 and link 41 to the extent that its abutment edge 38 rests against the abutment 35 of auxiliary looper shaft 9 which is now in the recess 37. If the lock member 23 (Figs. 1 and 2) now drops into the groove 25 of the brake disk 24 the machine is stopped immediately. As this release movement is carried out a further rotary movement is imparted to the dog 36 (Fig. 4) by the switch lever 18 which is now transferred to the auxiliary looper shaft 9 and thus to the auxiliary looper.

As a result of the axial displacement of the auxiliary looper 26 which has taken place previously this looper when rotating enters the loop 67 (Figs. 5 and 7) in such a manner that only one leg of the loop of the thread which is connected to the needle is gripped by the looper hook 27, while the other leg which extends from the material is seized by the cutter and is cut through. Since the thread is cut closely below the work material a sufiiciently great length of thread is available for forming the first stitch of a new series of stitches.

When switching the machine on (Fig. 3) the lock catch 16 of the switch lever 15 engages the lock member 17 of the switch lever 18 and holds it in inoperative position together with lock member 23. As the switch lever 18 ispivotally moved the double armed lever 57 is likewise shifted "by way of arm'63 and set screw 65 while tensioning the spring 60. This relieves the load from lever 51 and the auxiliary looper shaft 9 with auxiliary looper 26 is returned to normal sewing position by the spring 34 (Figs. 6 and 4). At the same time the dog 36 and the levers 41 and 43 associated with it are returned to their idle positions.

The sequence of operations will now be the same as described above. If it should be desired to tear the thread instead of cutting it this can be achieved in simple fashion by replacing the cutter with a hook or the like.

Having now described our invention with reference to the embodiment illustrated, we do not wish to be limited thereto, but what we desire to protect by Letters Patent is set forth in the appended claims.

We claim:

1. Thread cutting device for single thread chain stitch sewing machine of the type comprising a material support plate having a needle aperture, a drive shaft, a guiding disk for controlling'th'e operation of the machine-including carn means, abrake disk disposed endwise of said drive shaft havinga raised tapering portion and a slot, a doublearmed switch lever having a lock member at one end of one arm and having the other arm disposed in operative relation to said brake disk, a control lever in operative engagement at one end with said guiding disk and provided at the other end with a member adapted to interlock withsaid lock member, a looper mounted below said aperture endwise of a looper shaft disposed in the base of the machine and geared to said drive shaft, an auxiliary looper disposed adjacent said looper in operative relation thereto and mounted for rocking motion endwise of an auxiliary shaft disposed proximate said looper shaft, said auxiliary shaft including a spring biasing said auxiliary shaft in position of normal operatioma cam on" said looper shaft and a cam lever on said auxiliary shaft for imparting angular movement to said auxiliary looper, said auxiliary looper extending intermediate said aperture and said looper and presenting a hook on one side of its end and'a cutter on the side opposite said hook, said auxiliary shaft being axially movable against the bias of said spring to shift said auxiliary looper from a normal loop catching position to thread cutting position and a plurality of connected levers including a double armed lever having one arm operatively linked to said switch lever and the other arm disposed endwise of said auxiliary shaft operative under control of said brake disk to move said shaft axially against the bias of said spring in one direction and upon alignment of said end of said switching lever with said slot to permit axial movement of said shaft under the pressure of said spring in the opposite direction.

2. Thread cutting device for single thread chain stitch sewing machine of the type comprising a material support plate having a needle aperture, a drive shaft, a guiding disk for controlling the operation of the machine including cam'means, a brake disk disposed endwise of said drive shaft having a raised tapering portion and a slot, a double armed switch lever having a lock member at one end of one arm and having the other arm disposed in operative relation to said brake disk, a control lever in operative engagement at one end with said guiding disk and provided at'the other end with a member adapted to interlock with said lock member, a looper mounted below said aperture endwise of a looper shaft disposed in the base of the machine and geared to said drive shaft, an auxiliary looper disposed adjacent said looper in operative relation thereto and mounted for rocking motion endwise of an auxiliary shaft disposed proximate said looper shaft, said auxiliary shaft including a spring biasing said auxiliary shaft in position of normal operation, a cam on said looper shaft and a cam lever on said auxiliary shaft for imparting'angular movement to said auxiliary looper; said auxiliary looper extending intermediate sai d aperture and said looper and presenting a hook on one side of its end and a cutter on the side opposite said hook, said auxiliary shaft being axially movable against the bias of said spring to shift said auxiliary looper from a normal loop catching position to thread cutting position and a plurality of connected levers including a double armed lever having one arm operatively linked to said switch lever and the other arm disposed endwise of said auxiliary shaft operative under control of said brake disk to move said shaft axially against the bias of said spring in one direction and upon alignment of said end of said switching lever with said slot to permit axial movement of said shaft under the pressure of said spring in the opposite direction, and a dog rockably mounted around said auxiliary shaft having a recess presenting an abutment, an abutment member secured to said auxiliary shaft for engagement by said abutment, and a bell crank lever and a link operatively connecting said dog to said lock member on said switch lever.

3. Thread cutting device for single thread chain stitch sewing machine of the type comprising a material support plate having a needle aperture, a drive shaft, a guiding disk for controlling the operation of the machine including cam means, a brake disk disposed endwise of said drive shaft having a raised tapering portion and a slot, a double armed switch lever having a lock member at one end of one arm and having the other arm disposed in operative relation to said brake disk, a control lever in operative engagement at one end with said guiding disk and provided at the other end with a member adapted to interlock with said lock member, a looper mounted below said aperture endwise of a looper shaft disposed in the base of the machine and geared to said drive shaft, an auxiliary looper disposed adjacent said looper in operative relation thereto and mounted for rocking motion endwise of an auxiliary shaft disposed proximate said looper shaft, said auxiliary shaft including a spring biasing said auxiliary shaft in position of normal operation, a cam on said looper shaft and a cam lever on said auxiliary shaft for imparting angular movement to said auxiliary looper, said auxiliary looper extending intermediate said aperture and said looper and presenting a hook on one side of its end and a cutter on the side opposite said hook, said auxiliary shaft being axially movable against the bias of said spring to shift said auxiliary looper from a normal loop catching position to thread cutting position and a plurality of connected levers including a double armed lever having one arm operatively linked to said switch lever and the other arm disposed endwise of said auxiliary shaft operative under control of said brake disk to move said shaft axially against the bias of said spring in one direction and upon alignment of said end of said switching lever with said slot to permit axial movement of said shaft under the pressure of said spring in the opposite direction, and a dog rockably mounted around said auxiliary shaft having a recess presenting an abutment, an abutment member secured .to said auxiliary shaft for engagement by said abutment, a bell crank lever and a link operatively connecting said dog to said lock member on said switch lever, and set screws adjustable to preset the positions of said bell crank lever and said double armed levers disposed endwise of said levers and said bell crank lever and said double armed levers being spring biased in the direction of their inoperative positions.

References Cited in the file of this patent UNITED STATES PATENTS 1,228,871 Barron June 5, 1917 1,251,451 Fifield Dec. 25, 1917 1,291,335 Wood Jan. 14, 1919 1,514,609 Fifield Nov. 11, 1924 2,247,570 4 Clayton July 1, 1941 2,335,827 Gunther Nov. 30, 1943 

